Archive for the ‘Volcanoes’ category

Big Pictures: Space Shuttle and Mount St. Helens

May 18, 2010

The Big Picture has been on a roll lately, with two sets of particular interest to planetary and space-types. First, is the feature on the final launch of the space shuttle Atlantis last week:

Second, today is the 30th anniversary of the explosive eruption of Mount St. Helens, and there are some amazing photos that show the devastating power of a volcanic eruption:

Advertisements

LPSC 2010 – Day 4: Mars Oceans, Titan Lakes, Astrobiology and Asteroids

March 6, 2010

Thursday started off with a couple of talks about the possibility of oceans on Mars. The first one, given by Gaetano DiAchille looked at possible locations of deltas all over Mars to try to figure out the water level of a past ocean. Deltas form when a river hits a standing body of water and drops its sediment, so they are a reliable marker of the water level. DiAchille found that “open deltas” – that is, deltas that do not end in a closed basin like a crater, all appear at the same elevation. This might mean that they all fed into a large northern ocean.

A map of valley network density on Mars and the possible extent of a northern ocean.

In the second talk, Wei Luo described his work mapping where all of the valley networks on Mars are and found that the northern limit of the networks fits with elevations that had previously been considered as possible ocean shorelines. The valley networks also matched with locations that atmospheric models predict would get the most precipitation.

Neither of these studies is conclusive evidence for a northern ocean on Mars, but they are interesting and they suggest that the “ocean hypothesis” is becoming popular again after years of little interest.

Later that day I saw a talk by Nick Warner describing the possible thermokarst lakes that he discovered in Ares Vallis on Mars. I wrote an article on Universe Today about this discovery when it was first announced a couple months ago.

I ducked out of the Mars talks to go see a talk by my friend Debra Hurwitz about a lava channel in a crater in Elysium Planitia. The channel was formed when lava breached the rim of the crater, flowed down the inner wall and ponded in the bottom. She calculated that the lava probably flowed at about 17-35 meters per second and that 6,000 cubic meters per second flowed down the channel for about 15 days. She also found that the channel could have been eroded mechanically without the need for the lava to actually melt the underlying rock very much.

A sketch of the lava channel filling the crater in Elysium Planitia.

After that, I headed over to the Titan session to hear a talk by Ralph Lorenz about waves on Titan lakes. Most of what we know about the surface of Titan, including the presence of liquid hydrocarbon lakes, is based on radar images from Cassini that measure roughness. The lakes show up as perfectly smooth (and therefore dark) surfaces, which is weird because radar images of lakes on earth usually have slight roughness due to waves. On Titan the gravity is lower, so you would expect bigger waves. It’s possible the lack of waves is due to the viscosity of the lakes, which might be increased by bigger “tar-like” molecules dissolved in the thinner ethane and methane, but it might also be due to a lack of wind. The Cassini mission will be watching as the seasons at Titan change to see if the wind changes and kicks up any waves.

A (suggestively colored) radar map of lakes on Titan.

I did a lot of session hopping on Thursday! The next stop was the astrobiology session. Oleg Abramov presented some results of his investigation of what intense impacts might have done to early life on the earth or Mars. He found that even during the Late Heavy Bombardment, the crust is not sterilized by the impacts, and in fact it might be more habitable for early life because impacts deliver organic molecules and cause widespread hydrothermal activity!

The talks I was really interested in were two talks on the magnetite crystals discovered in the famous ALH84001 meteorite. I posted a while back about a new paper that claims these crystals are evidence of life on Mars, and these two talks were focused on the claim. The first talk, by Allan Treiman gave some good background on the debate over whether ALH84001 preserves evidence of life and then addressed some of the new claims about the magnetite crystals. He said that most of the attributes of biological magnetite crystals, such as their size, lack of flaws, and precise crystal structure were not observed in the ALH84001 crystals. The big question is why the crystals are so pure. Allan argued that you can get pure crystals just from the heating of iron carbonate, which is found in the meteorite.

The following talk was by Kathy Thomas-Kleptra, whose paper Treiman was responding to. She showed that Treiman had probably made an error in calculating the breakdown temperature for iron carbonate. She also pointed out that the crystals are found in carbonates without much iron and that there is no graphite observed, but it is also a byproduct of heating the carbonates.

I don’t know enough about petrology and geochemistry to know who is right here, and I was very disappointed that both Kathy and Allan used up all of their time talking, so there was no chance at all for questions! I wasn’t the only one. When the moderator said that there was not time for questions and that they had to get on with the next session, most of the room groaned and protested. But alas, the talks pressed onward.

Biogenic magnetite crystals inside a bacterium one Earth.

I zipped back over to the Titan talks in time to catch the end of one pointing to features that they claimed were “deltas” in one of the lakes. I was very skeptical of this because the quality of the radar images is so low. What they avtuall observe is a dark branching channel that ends at a peninsula in one of the lakes. That’s not evidence for a delta in my book. This talk made me realize how spoiled I am with HiRISE, CTX, MOC and other high-resolution data on Mars!

Finally, I stopped by the asteroid session for two talks. The first was by Dan Scheeres and he talked about the role that tiny forces might play in holding asteroids together. He showed that Van Der Waals forces, normally ignored for all but the tiniest particles, actually might be important in holding particles together in asteroids. He made the analogy to powders like flour or cocoa powder on earth. These can clump together and when they are stressed the form fractures even though they are made of loos grains. The same thing might happen on a much bigger scale with the gravel and boulders in low-gravity asteroids!

It's possible that the fractures in objects like Phobos are more like the cracks you see in flour than like cracks in a solid, fractured rock.

The last talk I caught on Thursday was by my friend Seth Jacobson, who showed some simulations of asteroids that spin so fast they break apart. He showed that the ratio of sizes between the two bodies make a big difference in how the binary asteroid evolves. In some cases, the secondary asteroid even swings so close to the primary that it splats apart and forms a short-lived three-body system!

Model Mars Landscapes!

January 25, 2010

Check out these spectacular new photos of Mars! It certainly looks like the rovers have stumbled upon some more interesting terrain! The only catch is, these aren’t pictures of Mars at all, they are photographs of models made of, among other things, paprika, chili powder, and charcoal. They are the work of Matthew Albanese, and you need to go check out some of his other photographs. There are steel-wool tornadoes, faux-fur fields, and this spectacular glowing volcano:

(Hat tip to Ann Martin, fellow Cornell Astronomer and blogger at the ALFALFA blog for sharing the link to these pictures!)

Lava Tubes on the Moon!

November 25, 2009

Image credit: JAXA/SELENE

Ever wonder how astronauts on the moon are going to avoid deadly space radiation? One option is to live in caves, and luckily the Kaguya team has found one! Read more about it in my article over at Universe Today.

Volcanic Explosion Seen From Space

July 1, 2009

This is completely awesome:

(Courtesy of Ian O’Neil and Richard Drumm)

Olympus Mons is How Tall?!

May 23, 2009

Olympus Mons is a big volcano. It is almost unimaginably huge. It is 550 kilometers (342 miles) across at its base, and the volcanic crater (the technical term is ‘caldera’) at the peak is 80 kilometers (53 miles) long. If you were standing at the edge of the caldera, the volcano is so broad and the slopes are so gradual that the base of the volcano would be beyond the horizon. That’s right, it is a volcano so big that it curves with the surface of the planet.

And it is tall. 27 kilometers tall. That’s 16.7 miles from base to summit. 88,600 feet. That’s about three times as tall as Mt. Everest. Even Mauna Kea, Earth’s own giant shield volcano doesn’t come close. Measured from the sea floor to its summit, Mauna Kea is 33,476 feet (10.2 km) tall: taller than Everest, but only about 40% the height of Olympus Mons.

The state of Hawaii, compered with Olympus Mons.

The state of Hawaii, compared with Olympus Mons.

Ok, so throwing those numbers around is fun if you like stats, but it still doesn’t convey quite how tall Olympus Mons is. So here’s an eye opener. Olympus Mons is so tall that it essentially sticks up out of Mars’s atmosphere. The atmosphere on Mars is thin to begin with, but at the summit of Olympus Mons, it is only 8% of the normal martian atmospheric pressure. That is equivalent to 0.047% of Earth’s pressure at sea level. It’s not quite sticking up into space, but it’s pretty darn close. In fact, it was first confirmed to be a huge mountain when Mariner 9 saw it towering above the top of a global dust storm like an island in a rust-colored sea.

Mariner 9 photograph of Olympus Mons towering above the clouds on Mars.

An airbrush painting of Olympus Mons towering above the clouds by Gorden Legg, a Hollywood artist, based on Viking Orbiter mosaic P17444.

Finally, since it is fun to compare Olympus Mons to Mauna Kea, what would the pressure be like at the summit if we placed Olympus Mons next to Mauna Kea in the Pacific? In that case, the summit of Olympus would be 21 km (68,897 ft) above sea level: still higher than Everest, and about twice as high as normal jets fly. The atmospheric pressure at the summit would be about 4.6% that at sea level. For comparison, at the top of Everest it is about one third the pressure at sea level, and most people still need to use oxygen canisters.

Olympus Mons is huge. Hopefully these numbers give you a little better idea of just how huge. If you’re wondering how it got to be so big, I already wrote about that in this post about shield volcanoes, so go check it out!

The tallest mountains on Mars, Earth, and Venus compared. Note that the horizontal scale is drastically squashed.

The tallest mountains on Mars, Earth, and Venus compared. Note that the horizontal scale is drastically squashed.

Big Pictures of Mount Redoubt Eruption

April 6, 2009

r06_1237756722

The Big Picture, an awesome photo-blog that you should be reading, has a very cool set of photos of the Mount Redoubt eruptions in Alaska. I thought it was especially cool to see how the glacier on top of the mountain is collapsing as it melts from beneath.

Update: Just like last time the Big Picture posted volcano photos, global warming deniers are posting in the comments and claiming that volcanoes make much more CO2 than humans, and therefore global warming is not man-made. Luckily, another commenter (#37) posted a very well-researched response on the Big Picture site. The Hawaii Volcano Observatory has also addressed this question: “Which Produces More CO2, Volcanic or Human Activity?”

The answer: on average, volcanoes produce less than 1% as much CO2 as fossil fuels do.